N.B. The
Gregorian calendar
currently in use in the United States reflects the Christian
heritage of Western Civilization. Year 1 AD (Anno Domini or “in the year of
the Lord”) marks the year of Christ’s birth (although Biblical historians
now believe this is probably off by five years). There is no year 0; the year
before Christ’s birth is 1 aCn (Ante Christum Natum or “before the birth of
Christ) or in English BC or “before Christ.”The abbreviations CE (Common Era) and BCE (Before
the Common Era) are also used for AD and BC respectively. In the Gregorian
calendar, the new year begins on January 1st.

The Gregorian
calendar replaced the Julian calendar in 1582 in most of the Roman Catholic
world, in 1752 in Great Britain
and her colonies, and in 1918 in Russia.
In the Julian calendar the new year began on March 25th.

Areas
of the world that have other religious traditions use other dating systems.
Israel
uses the traditional Hebrew calendar which dates from Creation (as figured
from the Bible). August 23, 2005 in the Gregorian calendar is 18 Av 5765 in
the Hebrew calendar.The Jewish New
Year on 4 October will be 5766 A.M. (Anno mundi or “year of the world”). In
the Islamic World Anno Hegirae or “in the year of the hijra” (marking Mohammed’s
flight from Mecca to Medina), year 1 dates from 622 CE.

Throughout
much of ancient and medieval history dates reflected important political developments
or the reigns of rulers. The Roman system, for instance, dated events from
the founding of Rome (753 BCE).England used regnal years concurrently
with the Julian calendar. The regnal year began the day of the ruler’s accession
to the throne. 1 Elizabeth I would run from 17 November 1558 to 16 November
1559; 2 Elizabeth from 17 November 1559 to 16 November 1560, etc. Thus, an
event dated 12 December 10 Elizabeth
I would have occurred on 12 December 1567.